An arrangement generally of this type is described in the German Offenlegungsschrift 29 26 268. This known arrangement serves for the determination of the instantaneous fuel consumption of internal combustion engines with fuel injection and ascertains the instantaneous fuel consumption from signals proportional to the rotational speed and the travelled distance and from a signal corresponding to the drive pedal position as well as from predetermined fuel consumption-engine rotational speed characteristic curves dependent on the drive pedal position and indicates this value of the instantaneous fuel consumption.
An installation is disclosed in the U.S. Pat. No. 4,244,210 in which a tachometer dial includes a predetermined number of light elements, of which each is coordinated to a predetermined dial partial range and by means of which the instantaneous fuel consumption is also indicated. Though the instantaneous fuel consumption provides an absolute value, no conclusions can be drawn therefrom as regards an economic driving manner since this value changes, for example, during the shifting into another speed. The specific fuel consumption provides in that case more unequivocal indications.
Many motor vehicles are series-equipped with tachometers, on the dial surface of which is printed a so-called economy field. This field which is characterized in color, is to provide an indication for fuel-favorable operating, respectively, rotational speed ranges of the engine. A similar arrangement operates by means of several light diodes of different color which light up if the rotational speed is located in the rotational speed ranges coordinated to these light diodes (Publication, "Elektor", November, 1980, page 45 et seq.). These indications refer to the engine rotational speed alone, and can be very inaccurate since the load condition of the engine (position of the control rack or of the throttle valve, or duration of the injection period) is not taken into consideration.